The overall objective of this study is to develop an optical coherence tomography (OCT) based high- resolution mouse embryonic brain imaging and analysis approach, and to use this method in correlation with molecular analysis to understand the interplay between ethanol (EtOH) and nicotine (NIC) effects on embryonic brain development. Maternal exposures to these substances are linked to fetal growth retardation and neurotoxicity, and these toxins often co-abused during pregnancy. However, studies on the combined fetal effects of NIC and EtOH are very limited and their combined effects on molecular mechanisms of fetal development, particularly the brain, are poorly understood. Therefore, there is a critical need to understand the interplay between the effects of EtOH and NIC via development of high-resolution imaging technique capable of live longitudinal analysis of developing brain. Intriguingly, our recent studies suggested that EtOH and NIC exert mutually antagonistic effects on fetal neuronal stem cells development. In this proposal, we will investigate if these toxins have indeed antagonistic or synergetic effects on embryonic brain development in live mouse embryos with implementation of an innovative higher-resolution embryonic brain imaging and dynamic quantitative analysis approaches, which we develop. We have pioneered OCT-based methodology for live in utero imaging and longitudinal phenotypic analysis of mouse fetuses in utero. Here we propose to further develop both the technology and the methodology for longitudinal brain imaging and analysis. The study is focused on the second trimester- equivalent period of development, when the neuronal stem cells give rise to most of the neurons of the adult brain. The central hypothesis of this proposal is that EtOH and NIC have partially antagonistic effects in fetal brain development. By successful accomplishment of the proposal, we will establish a live mouse embryonic brain imaging approach, will develop a set of protocols and detailed assessments to quantitatively characterize dynamic embryonic brain development with cellular resolution, and will investigate if EtOH and NIC synergize to disrupt the brain development or exhibit partially antagonistic effects. We will also assess the feasibility of using nicotinic receptor antagonists and agonists t prevent the individual and combined effects of EtOH and NIC. Therefore, studying this effect is highly significant from both fundamental biology and teratogenic points of view since it may have particular significant impact for the development of novel and innovative therapies for reversing teratology.